The present invention relates generally to liquid dispensing systems for dispensing liquid material onto an elongated strand and, more particularly, to a guide system for use with such a liquid dispensing system to guide the strand during the dispensing process.
In the manufacture of disposable diapers, adult incontinence pads and other hygienic articles, it is often desirable to provide a stretchable portion on the article, such as a waist band, leg cuff or other stretchable area, so that a relatively tight fluid seal between the article and the body can be formed. Generally, these stretchable portions are formed either by bonding stretched elastic strands directly to the fabric, or by bonding stretched elastic bands directly to a web of waist band or leg cuff material, for example, which is then bonded to selected areas of the article. The stretched elastic strands are bonding to the substrate substantially entirely along their respective axial lengths so that as the strands contract, the substrate is bunched together to form stretchable fabrics for use in a variety of products.
During the liquid dispensing process, the strands run continuously in a machine direction while the liquid dispensing system dispenses beads of adhesive toward the strands. Each bead may be dispensed in a swirl pattern toward a strand so that the pattern of the dispensed bead expands in the cross-machine direction. The dispensed pattern is controlled so that a portion of the bead crosses the travel path of the strand and attaches thereto.
Proper coating of the strands with adhesive material requires proper positioning of the strands relative to the dispensing outlets of the liquid dispenser. For example, if the distance between the strands and the dispensing outlets is too great, the dispensed adhesive beads will have pattern widths that will overshoot the edges of the strands so that portions or amounts of the dispensed adhesive material may be wasted. Also, if each strand is not generally aligned in the cross-machine direction with the axis of a respective dispensing outlet, the dispensed adhesive beads will not be applied symmetrically to the strand so that portions of the strand may not receive adhesive and therefore will not be properly laminated to the substrate.
In the past, a rotatable guide wheel has been mounted to the liquid dispensing system upstream of the dispensing outlets to guide the strands along travel paths spaced from the respective dispensing outlets. The guide wheel has circumferential grooves that engage and support the strands to guide the strands along their respective travel paths. In one known approach, the guide wheel is mounted to the liquid dispensing system through a rigid support arm that positions the guide wheel, and thus the travel paths of the strands, at fixed locations relative to the dispensing outlets. Therefore, no adjustability is provided to change the position of the strands relative to the dispensing outlets. In another known approach, the guide wheel is mounted to the liquid dispensing system through a linkage assembly having two (2) degrees of freedom that permits adjustments to be made in the position of the guide wheel in the machine direction, and in the distance between the strands and their respective dispensing outlets by raising or lowering of the guide wheel. Neither of these approaches provides manual adjustability of the positioning of the strands in the cross-machine direction so that the strands can be accurately and reliably aligned with the axes of their respective dispensing outlets to ensure proper coating of the strands prior to lamination.
Accordingly, there is a need for a guide system that improves the positioning of an elongated strand relative to a dispensing outlet of a liquid dispenser.
The present invention overcomes the foregoing and other shortcomings and drawbacks of guide systems and methods heretofore known for positioning elongated strands in a liquid dispensing environment. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
The guide system of the present invention positions one or more elongated strands of material relative to dispensing outlets of a liquid dispensing system. The strands may comprise elastic or non-elastic materials. Each strand travels along a travel path spaced from a respective dispensing outlet so that a bead of adhesive is fully or at least partially captured on the strand prior to the strand being bonded to a substrate.
The strands run continuously in a machine direction, and the liquid dispensing system is operable to dispense beads of adhesive toward the strands from the respective dispensing outlets. Each bead is preferably dispensed in a swirl pattern toward the strand so that the pattern expands in the cross-machine direction and a portion of the bead crosses the travel path of the strand and attaches thereto.
The guide system of the present invention includes a guide mechanism, preferably in the form of a rotatable wheel having circumferential grooves that are operable to guide the strands along travel paths generally in alignment with the respective dispensing outlets so that the travel path of each strand generally intersects the axis of a respective dispensing outlet. The guide system further includes a positioning mechanism operatively connected to the guide mechanism for positioning the guide mechanism along three (3) orthogonal axes, namely an X-axis in the machine direction, a Y-axis, and a Z-axis in the cross-machine direction. The guide system has three (3) degrees of freedom for positioning the guide mechanism along the three (3) orthogonal axes. The guide mechanism engages and supports the strands upstream of the dispensing outlets and controls the position of each strand along a Z-axis, i.e., the position of the strand in the cross-machine direction relative to the axis of a respective dispensing outlet, and along a Y-axis, i.e, the spacing or distance of each strand from a respective dispensing outlet. The positioning mechanism is operable to properly position the guide mechanism upstream of the dispensing outlets so that the position of the guided strands relative to the respective dispensing outlets can be accurately and reliably adjusted and controlled.